Button bit

ABSTRACT

A percussive rock drill bit of a type generally known in the art as a button bit wherein a plurality of wear-resistant metal inserts project from the working face of the drill bit. An elastomeric sleeve surrounds that portion of the sides of the insert which is embedded in the bit body. There is metal to metal contact be between the end of the insert and the bit body for transmitting blow energy from the bit body to the insert.

United States Patent 8 3,101 ,934 8/1963 Poundstone 175/410 X 3,318,4015/1967 Carbert 175/413 3,346,060 10/1967 Beyer 175/410 FOREIGN PATENTS183,787 3/1963 Sweden 175/410 Primary Examiner1an A. Calvert AssistantExaminer-Richard E. Favreau Attorneys-David W. Tibbott, Carl R. l-lortenand Frank H.

Thomson ABSTRACT: A percussive rock drill bit of a type generally knownin the art as a button bit wherein a plurality of wear-resistant metalinserts project from the working face of the drill bit. An elastomericsleeve surrounds that portion of the sides of the insert which isembedded in the bit body. There is metal to metal contact be between theend of the insert and the bit body for transmitting blow energy from thebit body to the insert.

PATENTEDHUV 9 197i 3,618.6 8 3 f l E INVENTOR ROBERT W. HUGHES ATTORNEYBUTTON BIT This invention relates to rock drill bits and in particularto rock drill bits generally known in the art as button bitsand to anovel means for securing the wear-resistant inserts in the bit body.

Percussive rock drill bits include a bit body with a plurality ofwear-resistant hard-metal inserts such as tungsten carbide projectingfrom the working face of the bit body. Button bits are a type ofpercussive rock drill bit in which there are a plu rality of generallycylindrical wear-resistant inserts embedded in the working face. The endof the insert which projects outwardly is rounded. Prior to thisinvention, button bits were manufactured by drilling aplurality of holesin the working face of the bit body. The tungsten carbide insertswereplaced in the holes and secured therein bymeans of brazing or by ashrink fit. Close tolerances must be kept in order to insure that theinserts are held in place when a shrink fit or a brazing technique isused. The proper relationship between the hole diameter and the size ofthe carbide insert must be maintained. If the spacing is too large, ashrink fit will not hold the insert in the bit body. Thus, it is oftennecessary to use a selective carbide insert assembly technique to insurethe proper spacial relation between the bit body and insert. If aninsert is oversized, it is necessary to insert that carbide intoanoversized hole. This increases labor costs andhence the cost ofthebit.

An additional disadvantage of prior methods of securing a carbide insertin the bit bodyis that heat treatment of the bit body must besubstantially eliminated. With the shrink fit method, the bit body isheated to expand the hole. The'insert is placed in the hole and the bodyis cooled. Any heat treatment of the bit body will be lost in thisprocess. In general,the bit body must be kept soft. This reduces thewear capabilities of the bit body.

A further disadvantage of the present methods of securing the carbideinserts in the bit body is that if the insert should come loose from thebit body while the bit is being used in the field, the insert cannot bereplaced in the field. If the insert is to be replaced in order to gainoptimum performance from the bit, the bit must be returned to thefactory for reconditioning and replacement of the missing insert.

With present methods of securing the insert in the bit body, fracture ofthe insert often occurs if placement is incorrect. It is believed thatthe rigid interface between the insert and the bit body which preventsany movement of the insert is a cause of many failures of the inserts,

SUMMARY It is therefore the principal object of this invention toprovide means for mounting a hard-metal insert in a drill bit body whichwill overcome the aforementioned disadvantages of prior mountingarrangements.

It is a further object of this invention to provide means for mounting ahard-metal insert in a drill bit body which will reduce manufacturingcosts.

It is another object of this invention to provide a drill bit which willpermit increased tolerances to thereby reduce bit manufacturing costs.

It is a still further object of this invention to provide mounting meansfor the hard-metal insert of a drill bit which will permit heattreatment of the bit body.

It is a still further object of this invention to provide drill bitinsert mounting means which provides a shock-absorbing function for theinsert.

In general, the foregoing and other objects will be carried out byproviding a cutting implement for use with a rock drilling machinecomprising: a bit body having a working face at one end; said workingface having a plurality of openings therein; a wear-resistant insertmounted in each of said openings so that there is intimate contactbetween one end of said insert and the bottom of the opening withinwhich it is mounted; and an elastomeric sleeve positioned between thesides of said insert and said bit body.

BRIEF DESCRIPTION OF THE DRAWING Theinvention will be described inconnection with the accompanying drawing wherein:

FIG. I is a sectional view of a rock drill bit embodying the presentinvention;

FIG. 2 is a fragmentary view on an enlarged scale of a portion of thedrill bit of FIG. 1; and

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 of the drawing thereis shown a percussive drill bit generally indicated at l of the type andgenerally known in the art as a button bit. As is well known in the art,the bit is adapted to receive an impact from a drilling machine (notshown) and be rotated to thereby drill a hole. The bit is provided witha working face 2 and an axial passage 3 for conducting fiuid such ascompressed air for blowing cuttings out of the hole being drilled.

The working face 2 of the bit 1' is provided with a plurality of blindbores 5 which are adapted to receive hard-metal inserts 10 made of asuitable material such as tungsten carbide.

conventionally, the drill bitis heated to expand the blind bores 5, theinserts 10 are placed in the bores 5 and the drill bit cooled.Contraction of the bit body around the insert secured the insert inplace. By the present invention, the insert 10 is held in the bore 5 bymeans of an elastomeric sleeve 12. The sleeve surrounds that portion ofthe sidewalls of the inserts which-isembedded in the bit body I. The endwall 11 of the insert 10 remains in intimate contact with the bit bodyso that when the drill bit receives an impact from the drilling machine,blow energy may be transmitted from the bit body I to the insert 10.

The elastomeric sleeve I2 may be of'any resilient material such asneoprene or the like. Preferably, the sleeve 12 is bonded to thetungsten carbide insert 10. If desired, the sleeve 12 may also becemented to the walls of the bore 5 by means of a suitable adhesive suchas the expoxi-type adhesive.

The diameter of the bore 5 should be smaller than the free outsidediameter of the sleeve 12 so that the sleeve 12 is compressed betweenthe insert 10 and the walls of the bore 5. Dimensional tolerances of thehole 5 and insert 10 need not be as close as with prior art arrangementsbecause the sleeve 12 will permit a larger or smaller clearance betweenthe insert and bore than is permitted with prior arrangements. This willreduce manufacturing costs because the necessity of using selectiveinsert assembling techniques can be substantially eliminated. Thecompressive preload of the sleeve 12 between the sidewalls of the insert10 and the walls of the bore 5 retains the insert 10 in the bore 5. Thesleeve 12 must be of sufficient thickness to retain the insert in thecavity by a friction fit and to provide sufficient flexibility tooptimize the stresses in both the sleeve and the bore between the insertand the sleeve and between the sleeve and the bit body. The sleeve I2serves three basic functions. First, it holds the insert in the bit bodythereby eliminating the shrink fit or brazing techniques presentlyemployed. Second, the sleeve 12 serves as a shock absorber tending toreduce failure of the insert. Third, the sleeve 12 serves to eliminatethe high initial stresses in both the insert and the bit body which arenormally associated with a shrink fit. With present methods of securingthe insert in the bit body, if the insert moves a slight amount duringimpact, stresses in the insert will be increased tending to causefracture of the insert. The resilient sleeve 12 will permit a slightmovement of the insert 10 relative to the bit body 1 without increasingstresses in either the bit body or the insert and hence tend to reducefailure of the inserts.

By the present invention, it will be possible to place the insert in thebit body while the bit body is cold. This will permit the bit body to beheat-treated in the desired manner before the insert is placed in thebit. Since the bit body can be heattreated to the desired extent, astronger bit body and thus longer lasting bit can be achieved. Priormethods did not permit heat treatment because of the heating requiredfor the shrink fit process. The bit body could not be heat-treated afterthe insert were in place because the inserts would come loose from thebit body.

From the foregoing it should be apparent that the objects of thisinvention have been carried out. The tolerances can be reduced becausethe elastomeric sleeve will expand and contract an amount which willpermit larger hole and insert size tolerances. Selective carbideinsertion is eliminated. Heat treatment can be performed on the bit bodythus insuring a longer lasting drill bit. Because a shrink fit orbrazing is not required, the inserts can be field replaced with a toolwhich permits easy insertion of the insert and sleeve.

1 Claim:

1. A cutting implement for use with a rock drilling machine comprising:

a bit body having a working face at one end;

said working face having a plurality of openings therein;

a wear-resistant insert mounted in each of said openings so that thereis intimate contact between one end of said insert and the bottom of theopening within which it is mounted; and

an elastomeric sleeve positioned only between the sides of said insertand said bit body.

2. The cutting implement of claim 1 wherein said elastomeric sleeve isbonded to said insert.

3. The cutting implement of claim 2 wherein said elastomeric sleeve isbonded to said bit body.

4. The cutting implement of claim 1 wherein said opening is a blindcylindrical bore having a diameter smaller than the free diameter ofsaid sleeve.

5. The cutting implement of claim 4 wherein said sleeve is bonded tosaid insert.

6. A rock drill bit comprising:

a bit body having a working face at one end;

a plurality of button-type wear-resistant inserts each having one endand at least a portion of its sides mounted in said bit body andprojecting outwardly from said working face, said one end directlycontacting said body; and

a resilient sleeve surrounding each of said inserts and positioned onlybetween the sides of said insert and said bit body.

7. The rock drill bit of claim 6 wherein said resilient sleeve is bondedto said insert.

8 The rock drill bit of claim 6 wherein the working face of said bitbody is provided with a plurality of blind bores having a diametersmaller than the diameter of said resilient sleeve and each of saidinserts and said sleeve are mounted in one of said bores.

9. The rock drill bit of claim 8 wherein said sleeve is bonded to saidinsert.

10. The rock drill bit of claim 9 wherein said sleeve is bonded to saidbit body.

1. A cutting implement for use with a rock drilling machine comprising:a bit body having a working face at one end; said working face having aplurality of openings therein; a wear-resistant insert mounted in eachof said openings so that there is intimate contact between one end ofsaid insert and the bottom of the opening within which it is mounted;and an elastomeric sleeve positioned only between the sides of saidinsert and said bit body.
 2. The cutting implement of claim 1 whereinsaid elastomeric sleeve is bonded to said insert.
 3. The cuttingimplement of claim 2 wherein said elastomeric sleeve is bonded to saidbit body.
 4. The cutting implement of claim 1 wherein said opening is ablind cylindrical bore having a diameter smaller than the free diameterof said sleeve.
 5. The cutting implement of claim 4 wherein said sleeveis bonded to said insert.
 6. A rock drill bit comprising: a bit bodyhaving a working face at one end; a plurality of button-typewear-resistant inserts each having one end and at least a portion of itssides mounted in said bit body and projecting outwardly from saidworking face, said one end directly contacting said body; and aresilient sleeve surrounding each of said inserts and positioned onlybetween the sides of said insert and said bit body.
 7. The rock drillbit of claim 6 wherein said resilient sleeve is bonded to said insert.8. The rock drill bit of claim 6 wherein the working face of said bitbody is provided with a plurality of blind bores having a diametersmaller than the diameter of said resilient sleeve and each of saidinserts and said sleeve are mounted in one of said bores.
 9. The rockdrill bit of claim 8 wherein said sleeve is bonded to said insert. 10.The rock drill bit of claim 9 wherein said sleeve is bonded to said bitbody.